Method and means for causing seism



April 17, 1962 R. w. MCELROY METHOD AND MEANS FOR CAUSING SEISM FiledSept. 18. 1958 'INVENTOR. R O Y W. M E L ROY ATTORNEY Filed Sept. 18,1958, Ser. No. 761,882

1 Claim. ((31.102-42) invention pertains to exploration of geologicalformations by seismic reflection etc.; and more particu- .larly to theproduction of seism.

, widely used ethod of geological exploration includes the production ofa-seismic wave which bounces or echoes from a particular sub-surfaceformation. These echoes are recorded by seismographs and by theinterpretation of the seismograms so produced; an indication may be hadof the underground formation. Customarily, the

seismic wave is produced by drilling a hole about a hundred feet belowthe surface of the earth and detonating an 7 explosive charge withintheearth.

L have invented a method ,of producing seism which makes it unnecessaryto drill a hole within the earth. Basically, it.5comprises a bottomplate which rests upon the earth and a heavier weight which setsupon-the bottom plate. An explosive charge is located between thesetwo'members. When the charge is detonated, an impact of large'magnitudeis caused upon the bottom plate forcing the earth downward, compressingit, because of the heavier upper weight.

An object of this invention is to produce seism.

Another object of this invention is to produce a single seismic wave sothat seismograms may be easily interpreted.

A further object of this invention is to achieve the above witha devicewhich is safe to operate, easy to use, and light in weight so that it iseasily portable.

- Still further objects are to achieve the above with a device that issturdy, compact, simple, and reliable, yet inexpensive and easy tomanufacture.

The specific nature of the invention as well as other objects, uses, andadvantages thereof will clearly appear from the following descriptionand from the accompanying drawing, in which:

FIGURE 1 is a sectional view of a device according to this invention.

FIGURE 2 is a plan View of the device shown in FIG- URE 1.

As may be seen in the accompanying drawings, one embodiment of thisinvention uses a device having cup shaped bottom 10. This bottom member10 has plane surfaced bottom 12 which is adapted to be set solidly uponthe earth. Along the exterior of the sides of the cup shaped member arehandles 14 for dragging the device along the ground. 7

The inside of the cup shaped member 10 has an axial cylindrical bore 16.The upper inner lip is beveled at 18 for purposes which will bedescribed later. Concentric with the bottom is boss 20 which has rod 22threaded into it, so that the rod 22 extends upwardly co-axial with thebottom portion. An annular concavityt24 is cut Within the bottom memberaround the boss 20. This concavity is filled with an explosive charge 26when the device is m use.

By means of a radial bore through the bottom member detonator 28 isintroduced. It is contemplated that an electrical detonator would beused and the explosive charge be detonated with the aid of battery 30and switch 32. As explosive charges and detonators (either electrical,mechanical, or otherwise) are well known to the art, they have not beendescribed in detail here. The choice of the particular type of explosiveto be used, the amount of the explosive charge, and the type ofdetonator are all well within the skill of the one ordinarily skilled inthe art.

' shaped bottom member.

I upon the boss.

[-2 Upper member 34 is, partially seated within the cup The upper member34 is generally cylindrical in shape and has a reasonably snug fit withthe lower member 16. The upper. member has.

an bore in which the rod 22 is located. Also the upper memberhas anaxial depression which mates with boss 20. The depth of this depressionis less-than the height-of the boss, therefore the upper member restsbottom of the upper member and the upper portionvof the bottom. of thecup-shaped member. When the upper member. is in the lower position 'asillustrated, it does not rest upon the explosive charge .or any bits ofthe explosive charge which might be spread around. The upper member alsohas-handles '36 by which it may be moved;

Spring catches 38 are attached to the top of the upper member. Thesecatches are means .for retaining the upper member in a separatedposition after the, upper and lower members have been blown apart by theexplosive charge. They are firmly attached to the upper member by anyconvenient means such as welding or bolting.

' They have catch 44 at the top which is'supported by leaf spring 42.which extends parallel to the axis of the device.

Loop 44 is on the extreme upper portion of the rod 22 so that a hook maybe engaged therein to lift the device by power mechanism. Immediatelybelow this loop, the rod is of greater diameter than the lower portionof the rod. This portion of greater diameter is threaded so that a stop46 may be adjustably attached thereto. The stop 46 is a disk shapedmember. The diameter of the disk is slightly greater than the distancebetween the catches 44) when the leaf springs 42 are in the relaxedposition. Therefore as the upper member moves up, the upper'surface ofthe catches dllwill act as cams and spread the catches apart as theymove over to stop 46. However, as the upper member attempts to movedownward, the lower edges of the catches will stopon the disk 46 andretain the upper member in a separated position from the lower member.

The remote ends of the catches 40 are in the form of handles 48. If itis desired to separate the upper and lower members other than by theexplosive charge, the handles may be used for this purpose, preferablyin conjunction with power equipment. Alternately, the disk stop 46 maybe screwed down to its lowest position and the catches 40 snapped overit in this position. Then by rotating the disc along with the uppermember, the upper and bottom member can be separated.

Helical compression spring 50 encircles the rod '22 and normally restsupon the top of the upper member, and extends to bottom of the stop.When the explosive charge separates the upper and lower members, thespring will 'of the explosive charge detonating while the second soundwave would be produced when the upper member dropped back upon the lowermember.

It is necessary that the upper member have greater mass than the bottommember. Otherwise, the device would act as a launching for a projectileand the greater amount of energy would be expended in sending the uppermember up. However, by making the upper member of greater mass, thegreater amount of energy is expended in forcing the lower. member downwhich gives a greater impact and seism.

There is a definite clearance between the,

The lower edge of the upper member is beveled at 52. The gases resultingfrom the explosion of the charge will escape in an upward manner whenthe bevels 18 and 52 become aligned. If it were not for these 'bevels,most of the gases would be dissipated in an horizontal direction. Rathergood confinement of the explosion is obtained even though the top memberdoes not fit tightly within the cup shaped member nor around thesectional rod 22. There is not a straight line escape route for thegases. The gases from the explosive charge 46 must turn a corner alongany route in order to escape.

With this device, a simple mechanism has been provided for producingseism. It is relatively lightweight and easily transported by a smalltruck. Indeed it may be transported by helicopter or blimp to extremelyremote areas in rough terrain making possible geophysical explorationwhere otherwise it would not be economically feasible to use groundvehicles.

It will be apparent that the embodiment shown is on the exemplary andthat various modifications can be madein construction, materials, andarrangement within the scope of the invention as defined in the appendedclaim.

I claim as my invention:

A means for causing seism: a rigid cup shaped bottom member, a rigidupper member seated partially within said bottom member, said uppermember having a greater mass than said bottom member, an explosivecharge within said bottom member between the two members, means fordetonating the explosive charge, guide means attached to the lowermember for guiding the upper member, said means for guiding including arod extending from about the axis of the cup shaped bottom member, theupper member having a hole through which the rod extends, a stop on therod for limiting the movement of the upper member, the stop being a discshaped element threaded onto the rod, a helical compression springsurrounding the rod between the bottom member and the stop, and catchmeans attached to the upper member in operative relationship to the stopfor retaining the upper member in a separated position; so that when thebottom mem-' her is placed solidly upon the earthand the chargedetonated a seismic wave is produced within the earth resulting fromonly one impact.

References Cited in the file of this patent UNITED STATES PATENTS

